Posted: Sun Jan 06, 2008 4:47 pm |
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Concrete hardens in a few hours in the summer, and overnight otherwise. Working in freezing weather is bad practice. Adding salts to your water to lower the freezing point is questionable at best. Salt will weaken and ultimately destroy concrete, as well as corrode internal steel reinforcements. (For this reason, you should never use ocean beach sand or pebbles as aggregate.) Take off the mold only when the casting is really hard. Wet the surface then and often, for several days. Wrapping the casting in wet burlap is recommended, as this will help retain the moisture essential to the concrete's curing. It will keep strengthening over time. Its strength is commonly measured after 28 days (although it will keep getting stronger for years, if kept moist). Pour a test cylinder at the same time you pour a statue if testing will be required.
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